This invention relates to the mounting of cutting wheels, particularly as used in web processing machines for the purpose of slitting or perforating one or more webs longitudinally as the web moves between the cutting wheel and a backup device such as an anvil roller.
While there are many applications of such devices, cutting and/or longitudinal perforating wheels of this type are particularly used in connection with the manufacture of business forms, either in business forms presses or in collators for assembling multi-part business forms. Examples of such presses and collators are disclosed and described in U.S. Pat. No. 4,177,730 issued Dec. 11, 1979 and U.S. Pat. No. 3,727,908 issued Apr. 17, 1973 both of which are owned by the assignee of this application.
The cutting wheels must make a precise sharp cut (slit or perforation) in the web, and since the web or webs upon which the cutting wheels act may often be moving past the wheels at speeds in the order of 500 to 1000 Ft. per minute, or more, there is a need to replace the wheels for sharpening and other maintenance purposes. In addition, a particular job requirement may call for different types of perforations, requiring substitution of perforating wheels having different teeth dimensions. Therefore, it is desirable to provide a mounting for such cutting wheels which enables quick release of the cutting wheel from the freely rotatable shaft upon which the wheel is supported.
For many years slitter wheel holders have been available to the business forms manufacturing art, in which the holder comprises a block mounted on a cross rod or tube which extends transversely of the web being processed, the block being adjustable along the cross rod to select any desired position of the slitter wheel within the width of the web. On this block there is a pivoted arm which can move within limits toward and away from the web, and which preferably is spring loaded toward the web, and a circular housing is threaded into the end of the arm, allowing a limited adjustment of the housing within the end of the arm to permit a precise or fine adjustment of the slitter wheel position with respect to the arm and the holder block. This housing also contains bearings which support a shaft that is free to rotate in the bearings, and contains a collet over which a slitter wheel can be placed. A typical rod with a tapered end extends through the collet and the shaft, and can be tightened by a nut at the opposite end of the housing from the collet, to expand the collet and grip the cutting wheel. Once the wheel is in place and the fine adjustment (if any) is made, there is a hand operated clamping bolt which can be tightened to cause the end of the arm to tighten around the threads on the housing, maintaining the adjusted position of the parts.
In order to replace the cutting wheel in such devices it is necessary to have a set of tools, one to retain the position of the central rod and the other to loosen, and then tighten, the nut at the end of the rod, so as to allow the collet to contract to free the wheel, and then to expand to grip the next wheel. This requires the operator to keep these tools, usually an Allen wrench and an open end wrench available for his use in making this change, and in addition should it be necessary to adjust the position of the block along the supporting rod, an additional wrench of a different size, usually a larger Allen wrench to fit the larger socket head bolts in the block, is also required. Finally, in spite of the best efforts of the operator to secure the cutting wheels on the collet, these are subjected to substantial forces in operation. Web speeds in the order of 1000 Ft. per minute or more are common, and the freely rotating slitter wheels tend to rotate at comparable speeds, while being forced against the web or webs, usually working against an anvil roll or cylinder, while making the required perforations or continuous slits in the web. If the collet is not securely expanded to lock the wheel thereon, it is possible for the wheel to work loose and disengage from the holder, while rotating at substantial speed. This of course could present considerable danger since the wheels are, in general, steel discs with a sharp rim or edge, several inches in diameter.
Efforts have been made to reduce makeready time on business forms presses and collators, and the method and system described in the aforementioned U.S. Pat. No. 4,177,730 represents the first concerted effort to reduce makeready on an overall basis. Time studies with machinery of this type have indicated that when the press operator is required to utilize tools to dismount and re-mount slitter wheels, and to adjust the lateral register of the slitter wheel and holder, an average of six minutes is required to perform the necessary functions. It has also been discovered that as many as ten to fifteen cutting wheel changes per eight hour shift may be required, and thus it follows that it is possible that the operator might be required to devote as much as sixty to ninety minutes per shift just for the function of makeready of the cutting wheels or slitters.